Semiconductor devices are used in a large number of electronic devices, such as computers, cell phones, and others. Semiconductor devices comprise integrated circuits (ICs) that are formed on semiconductor wafers by depositing many types of thin films of material over the semiconductor wafers, and patterning the thin films of material to form the integrated circuits. The ICs include field-effect transistors (FETs), such as metal-oxide-semiconductor field-effect transistors (MOSFETs).
One of the goals of the semiconductor industry is to continue shrinking the size and increasing the speed of individual MOSFETs. To achieve these goals, three dimensional (3-D) or non-planar transistor structures such as fin FETs (FINFETs), multiple gate transistors, or gate-all-around transistors are being investigated for use in sub 22 nm transistor nodes. Such transistors not only improve area density, but also improve gate control of the channel.
However, fabrication of the FINFETs is complex and requires overcoming a number of challenging problems. One of the challenges is forming recess-free isolation structures. These recesses can be formed in a dielectric material in the early stages of forming the isolation structure. FIGS. 1A-C show cross-sectional views of a plurality of conventional isolation structures 120 for FINFETs 100 having recesses 126b present in the isolation structures 120 at various stages of fabrication. FIG. 1A illustrates the plurality of isolation structures 120 may be formed by etching a substrate 102 to form a plurality of trenches 122 separating a plurality of fin structures 110, then filling the plurality of trenches 122 with a dielectric material 124 (shown in FIG. 1B), such as high-density plasma (HDP) oxides, tetraethoxysilane (TEOS) oxides, or the like. The dielectric material 124 may comprise a plurality of deep slims/recesses 126a due to the high aspect ratio of the plurality of trenches 122. FIG. 1C shows a plurality of recesses 126b in the plurality of isolation structures 120 may be formed along the plurality of deep slims/recesses 126a during and after removing the upper portions of the dielectric material 124. The plurality of recesses 126b is problematic in various respects. For example, the plurality of recesses 126b present in the plurality of isolation structures 120 can become a receptacle of polysilicon and/or metals during subsequent processing thereby increasing the likelihood of device instability and/or device failure.
Accordingly, what is needed is an isolation structure for a FINFET having no recess.